1. Field of the Invention
The present invention generally relates to a pumping circuit for multiple nonvolatile memories and, more particularly, to a pumping circuit for an integrated circuit (IC) comprising a plurality of electrically erasable nonvolatile storage devices such as electrically erasable programmable read-only memories (EEPROM's) and flash memories. The pumping circuit uses a common voltage pump to provide a plurality of nonvolatile storage devices with a high voltage source so as to minimize the layout area and the cost.
2. Description of the Prior Art
As electrically erasable nonvolatile storage devices a plurality of electrically erasable nonvolatile storage devices such as electrically erasable programmable read-only memories (EEPROM's) and flash memories perform write/erase operations, a high-voltage source is required. Generally, a high voltage supplying circuit is used as a voltage pump to perform the write/erase operations.
When at least two electrically erasable nonvolatile storage devices with different functions are disposed in an IC, the IC generally comprises at least two voltage pumps because the high-voltage source is varied for different output conditions.
This kind of voltage pump provides the high voltage only when the nonvolatile storage devices perform write/erase operations. In an IC, the nonvolatile storage devices mostly perform read operation and thus the voltage pump idles for most of the time. Moreover, the voltage pump occupies a considerable amount of the layout area and the manufacturing cost is high.
Therefore, there exists a need in providing a pumping circuit for multiple nonvolatile memories using a common voltage pump to provide a plurality of nonvolatile storage devices with a high voltage source so as to minimize the layout area and the cost.